Plasma arc torches are widely used for cutting and marking metallic materials. A plasma arc torch generally includes a torch body, an electrode (i.e., a cathode) mounted within the body, passages for cooling and arc control fluids, a swirl ring to control the fluid flow patterns, a nozzle (i.e., an anode) with a central exit orifice, electrical connections, and a power supply. The torch produces a plasma arc, which is a constricted ionized jet of a plasma gas with high temperature and high momentum. A shield may also be employed to provide a shield gas flow to the area proximate the plasma arc. Gases used in the torch can be non-reactive (e.g., argon or nitrogen), or reactive (e.g., oxygen or air).
In operation, a pilot arc is first generated between the electrode and the nozzle. The pilot arc ionizes gas passing through the nozzle exit orifice. As the ionized gas reduces the electrical resistance between the electrode and the workpiece, the arc transfers from the nozzle to the workpiece. The torch may be operated in this transferred plasma arc mode, which is characterized by the conductive flow of ionized gas from the electrode to the workpiece, for the cutting of the workpiece.
Cooling consumables (e.g., the nozzle) of a plasma arc torch with a cooling liquid (e.g., water) can have safety and performance benefits. Without liquid cooling, the consumables can reach extremely high temperatures that can pose a safety issue during use. A lossless cooling system can allow the use of a dry plasma and a dry cutting table. Dry tables can be desirable due to the reduced mess and elimination of the need to dispose of the used/contaminated water, which can be considered to be hazardous waste.